[Tilesathome] New preprocessor - area center

[Rob Reid]

Jiri Klement wrote the following on 12/09/2008 01:47:
> I've added the area center preprocessor to svn. For now it's used only
> by XSLT. XSLT use different algorithm for area center calculation than
> orp, so problems with neighbouring tiles described by spaeth already
> exists for XSLT users. So not big deal if Java is not available and
> area-center preprocessor can't be used.
To me it does seem like a big deal, surely if we have a process that is 
know to cause inconsistencies in the map we should be trying to fix it 
not implement an additional process that adds more inconsistencies 
depending on what software clients have installed.
The idea of a preprocessor for this seems like a good one to me 
providing its output is used in both orp and XSLT and resolves the 
inconsistency. I got the impression from when Knut did the area center 
algorithm in XSLT that it was a pain to implement and I imagine it would 
be as much pain again to refine it with any improvements to the 
algorithm so moving this process into the preprocessing stage where we 
can chose what language to implement it in seems sensible.
One of the stated goals on the 'Things to do page' 
<http://wiki.openstreetmap.org/index.php/Things_To_Do#Task:_Unified_Preprocessor>  
(I know its a bit out of date) is to move towards a unified preprocessor 
so having one preprocessor that closes areas and calculates area centre 
in one pass would be great.

If a new process reduces map inconsistencies and does not complicate the 
whole chain then even if it is implemented in language that introduces 
extra dependencies surely we can live with it providing the implementer 
is prepared to maintain it?

Obviously I'm currently proficient in neither perl or java so as someone 
who can't contribute to the solution maybe my comments are out of line 
however what I do try to spend my time doing it fixing stuff that makes 
the map 'look bad' like incorrect ocean tiles or broken coastlines. From 
my point of view anything that can be done to reduce any inconsistencies 
between tiles rendered with or/p or osmarender and Inkscape or Batik is 
a good thing.

rcr